Polymers, resist compositions and patterning process

ABSTRACT

A resist composition comprising a base polymer having a fluorinated sulfonate or fluorinated sulfone introduced therein is sensitive to high-energy radiation below 300 nm, has excellent transparency, contrast and adherence, and is suited for lithographic microprocessing.

[0001] This invention relates to polymers useful as the base resin inresist compositions suited for microfabrication. It also relates toresist compositions, especially chemical amplification resistcompositions comprising the polymers, and a patterning process using thesame.

BACKGROUND OF THE INVENTION

[0002] In the drive for higher integration and operating speeds in LSIdevices, the pattern rule is made drastically finer. The rapid advancetoward finer pattern rules is grounded on the development of aprojection lens with an increased NA, a resist material with improvedperformance, and exposure light of a shorter wavelength. To the demandfor a resist material with a higher resolution and sensitivity, chemicalamplification positive working resist materials which are catalyzed byacids generated upon light exposure are effective as disclosed in U.S.Pat. Nos. 4,491,628 and 5,310,619 (JP-B 2-27660 and JP-A 63-27829). Theynow become predominant resist materials especially adapted for deep UVlithography.

[0003] Also, the change-over from i-line (365 nm) to shorter wavelengthKrF laser (248 nm) brought about a significant innovation. Resistmaterials adapted for KrF excimer lasers enjoyed early use on the 0.30micron process, passed through the 0.25 micron rule, and currentlyentered the mass production phase on the 0.18 micron rule. Engineershave started investigation on the 0.10 micron rule or less, with thetrend toward a finer pattern rule being accelerated.

[0004] For ArF laser (193 nm), it is expected to enable miniaturizationof the design rule to 0.13 μm or less. Since conventionally used novolacresins and polyvinylphenol resins have very strong absorption inproximity to 193 nm, they cannot be used as the base resin for resists.To ensure transparency and dry etching resistance, some engineersinvestigated acrylic and alicyclic (typically cycloolefin) resins asdisclosed in JP-A 9-73173, JP-A 10-10739, JP-A 9-230595 and WO 97/33198.

[0005] With respect to F₂ laser (157 nm) which is expected to enablefurther miniaturization to 0.10 μm or less, more difficulty arises ininsuring transparency because it was found that acrylic resins which areused as the base resin for ArF are not transmissive to light at all andthose cycloolefin resins having carbonyl bonds have strong absorption.It was also found that poly(vinyl phenol) which is used as the baseresin for KrF has a window for absorption in proximity to 160 nm, so thetransmittance is somewhat improved, but far below the practical level.

[0006] Since carbonyl groups and carbon-to-carbon double bonds haveabsorption in proximity to 157 nm as mentioned above, reducing thenumber of such units is contemplated to be one effective way forimproving transmittance. It was recently found that the transmittance inthe F₂ region is outstandingly improved by introducing fluorine atomsinto base polymers.

[0007] It was reported in SPIE 2001, Proceedings 4345-31, “Polymerdesign for 157 nm chemically amplified resists” that in resistcompositions comprising a copolymer of tert-butylα-trifluoromethylacrylate with5-(2-hydroxy-2,2-bistrifluoromethyl)ethyl-2-norbornene and a copolymerof tert-butyl α-trifluoromethylacrylate with4-(2-hydroxy-2,2-bistrifluoromethyl)methylstyrene, the absorbance of thepolymer at 157 nm is improved to about 3. However, these resins arestill insufficient in transparency because it is believed that anabsorbance of 2 or less is necessary to form a rectangular pattern at afilm thickness of at least 2,000 Å through F₂ exposure.

SUMMARY OF THE INVENTION

[0008] An object of the invention is to provide a novel polymer having ahigh transmittance to vacuum ultraviolet radiation of up to 300 nm,especially F₂ (157 nm), Kr₂ (146 nm), KrAr (134 nm) and Ar₂ (126 nm)excimer laser beams, and useful as the base resin in a resistcomposition. Another object is to provide a resist composition, andespecially a chemical amplification resist composition, comprising thepolymer, and a patterning process using the same.

[0009] It has been found that when a polymer having a fluorinatedsulfonate or fluorinated sulfone introduced therein is used as a baseresin, the resulting resist composition, especially chemically amplifiedresist composition is drastically improved in contrast and adhesionwithout detracting from transparency.

[0010] In a first aspect, the present invention provides a polymercomprising recurring units each having a functional group of thefollowing general formula (1), and having a weight average molecularweight of 1,000 to 500,000.

[0011] Herein R¹ is a methylene group, oxygen atom, sulfur atom or SO₂,R² to R⁵ each are hydrogen, fluorine, a straight, branched or cyclicalkyl or fluorinated alkyl group of 1 to 20 carbon atoms, —R⁶—SO₃R⁷ or—R⁶—SO₂R⁷, at least one of R² to R⁵ containing —R⁶—SO₃R⁷ or —R⁶—SO₂R⁷,R⁶ is a valence bond or a straight, branched or cyclic alkylene orfluorinated alkylene group of 1 to 20 carbon atoms, R⁷ is fluorine or astraight, branched or cyclic fluorinated alkyl group of 1 to 20 carbonatoms which may contain a hydrophilic group such as hydroxyl, and “a” is0 or 1.

[0012] In a preferred embodiment, the recurring units are recurringunits of either one of the following general formulae (2a) to (2d).

[0013] Herein R⁸ to R¹⁰ and R¹⁸ to R²⁰ each are hydrogen, fluorine or astraight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 20carbon atoms, R¹¹ is a group of the above formula (1), R¹² is amethylene group, oxygen atom, sulfur atom or SO₂, R¹³ to R¹⁶ each arehydrogen, fluorine, —R¹⁷—OR¹¹, —R¹⁷-Co₂R11 or a straight, branched orcyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms, atleast one of R¹³ to R¹⁶ containing —R¹⁷—OR¹¹ or —R¹⁷—CO₂R¹¹, R¹⁷ and R²¹each are a valence bond or a straight, branched or cyclic alkylene orfluorinated alkylene group of 1 to 20 carbon atoms, R²² is a straight,branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms, b is0 or 1, c is 1 or 2, and d is an integer of 0 to 4, satisfying 1≦c+d≦5.

[0014] In a second aspect, the invention provides a polymer comprisingrecurring units of the following general formula (3) and having a weightaverage molecular weight of 1,000 to 500,000.

[0015] Herein R²³ is a methylene group, oxygen atom, sulfur atom or SO₂,R²⁴ to R²⁷ each are hydrogen, fluorine, —R²⁸—SO₂F, —R²⁸—SO₃R²⁹ or astraight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 30carbon atoms, at least one of R²⁴ to R²⁷ containing —R²⁸—SO₂F or—R²⁸—SO₃R²⁹, R²⁸ is a valence bond or a straight, branched or cyclicalkylene or fluorinated alkylene group of 1 to 20 carbon atoms, R²⁹ isan acid labile group, an adhesive group or a straight, branched orcyclic fluorinated alkyl group of 1 to 20 carbon atoms which may containa hydrophilic group such as hydroxyl, and e is 0 or 1.

[0016] In preferred embodiments of the first and second aspects, thepolymer further includes recurring units of the following generalformula (4).

[0017] Herein R³⁰ is a methylene group, oxygen atom, sulfur atom or SO₂,R³¹ to R³⁴ each are hydrogen, fluorine, —R³⁵—OR³⁶, —R³⁵—CO₂R³⁶ or astraight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 20carbon atoms, at least one of R³¹ to R³⁴ containing —R³⁵—OR³⁶ or—R³⁵—CO₂R³⁶, R³⁵ is a valence bond or a straight, branched or cyclicalkylene or fluorinated alkylene group of 1 to 20 carbon atoms, R³⁶ ishydrogen, an acid labile group, an adhesive group or a straight,branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms whichmay contain a hydrophilic group such as hydroxyl, and f is 0 or 1.

[0018] The recurring units of formula (4) typically have a structure ofthe following formula (4a) or (4b).

[0019] Herein R³⁶ is as defined above, R³⁷ to R⁴⁰ each are hydrogen,fluorine or an alkyl or fluorinated alkyl group of 1 to 4 carbon atoms,at least either one of R³⁷ and R³⁸ contains at least one fluorine atom,and at least either one of R³⁹ and R⁴⁰ contains at least one fluorineatom.

[0020] In a preferred embodiment, the polymer further includes recurringunits of the following general formula (5).

[0021] Herein R⁴¹ is hydrogen, fluorine or a straight, branched orcyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms, R⁴² isa valence bond or a straight, branched or cyclic alkylene or fluorinatedalkylene group of 1 to 20 carbon atoms, R⁴³ is hydrogen or an acidlabile group, R⁴⁴ is fluorine or a straight, branched or cyclicfluorinated alkyl group of 1 to 20 carbon atoms, g is 1 or 2, and h isan integer of 0 to 4, satisfying 1≦g+h≦5.

[0022] The recurring units of formula (5) typically have the followingformula (5a) or (5b).

[0023] Herein R⁴³ is as defined above, R⁴⁵ to R⁵⁰ each are hydrogen,fluorine or an alkyl or fluorinated alkyl group of 1 to 4 carbon atoms,at least either one of R⁴⁵ and R⁴⁶ contains at least one fluorine atom,at least either one of R⁴⁷ and R⁴⁸ contains at least one fluorine atom,and at least either one of R⁴⁹ and R⁵⁰ contains at least one fluorineatom.

[0024] In a preferred embodiment, the polymer further includes recurringunits of the following general formula (6).

[0025] Herein R⁵¹ to R⁵³ each are hydrogen, fluorine or a straight,branched or cyclic alkyl or fluorinated alkyl group of 1 to 20 carbonatoms, and R⁵⁴ is hydrogen, an acid labile group, an adhesive group or astraight, branched or cyclic fluorinated alkyl group of 1 to 20 carbonatoms which may contain a hydrophilic group such as hydroxyl. In formula(6), R⁵³ is typically trifluoromethyl.

[0026] In a third aspect, the present invention provides a resistcomposition comprising the polymer defined above, preferably achemically amplified positive resist composition comprising (A) thepolymer defined above, (B) an organic solvent, and (C) a photoacidgenerator. The resist composition may further include (D) a basiccompound and/or (E) a dissolution inhibitor.

[0027] In a fourth aspect, the present invention provides a process forforming a resist pattern comprising the steps of applying the resistcomposition onto a substrate to form a coating; heat treating thecoating and then exposing it to high-energy radiation in a wavelengthband of 100 to 180 nm or 1 to 30 nm through a photomask; and optionallyheat treating the exposed coating and developing it with a developer.The high-energy radiation is typically an F₂ laser beam, Ar₂ laser beamor soft x-ray.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Polymer

[0029] For improving the transmittance in proximity to 157 nm, reducingthe number of carbonyl groups and/or carbon-to-carbon double bonds iscontemplated to be one effective way. It was also found that introducingfluorine atoms into base polymers makes a great contribution to improvedtransmittance. In fact, poly(vinyl phenol) having fluorine introduced inits aromatic rings offers a transmittance nearly on a practicallyacceptable level (see JP-A 2001-146505). However, this base polymer wasfound to turn to be negative upon exposure to high-energy radiation asfrom an F₂ excimer laser, interfering with its use as a practicalresist.

[0030] In contrast, those polymers obtained by introducing fluorine intoacrylic resins or polymers containing in their backbone an alicycliccompound originating from a norbornene derivative were found to have ahigh transparency and eliminate the negative turning problem. However,an increased rate of introduction of fluorine into a resin to enhancethe transparency thereof tends to compromise the adhesion of resin tosubstrate or the penetration of a developer. The present invention hassucceeded in overcoming the above-described deficiencies withoutdetracting from transparency, by introducing into a base polymer afluorinated sulfonate or fluorinated sulfone featuring excellentsubstrate adhesion and developer penetration.

[0031] According to the invention, using polymers or high molecularweight compounds comprising recurring units of the following generalformulae (2a) to (2d) having a unit of formula (1) incorporated thereinor recurring units of the following general formula (3), resistcompositions can be formulated which have improved substrate adhesionand developer penetration while maintaining high transparency at 157 nm.

[0032] Herein, R¹ is a methylene group, oxygen atom, sulfur atom or SO₂.R² to R⁵ each are hydrogen, fluorine, a straight, branched or cyclicalkyl or fluorinated alkyl group of 1 to 20 carbon atoms, —R⁶—SO₃R⁷ or—R⁶—SO₂R⁷. At least one of R² to R⁵ should contain —R⁶—SO₃R⁷ or—R⁶—SO₂R⁷. R⁶ is a valence bond or a straight, branched or cyclicalkylene or fluorinated alkylene group of 1 to 20 carbon atoms. R⁷ is afluorine atom or a straight, branched or cyclic fluorinated alkyl groupof 1 to 20 carbon atoms which may contain a hydrophilic group such ashydroxyl.

[0033] R⁸ to R¹⁰ and R¹⁸ to R²⁰ each are a hydrogen atom, fluorine atomor a straight, branched or cyclic alkyl or fluorinated alkyl group of 1to 20 carbon atoms. R¹¹ is a group of the above formula (1). R¹² is amethylene group, oxygen atom, sulfur atom or SO₂. R¹³ to R¹⁶ each are ahydrogen atom, fluorine atom, —R¹⁷—OR¹¹, —R¹⁷—CO₂R¹¹ or a straight,branched or cyclic alkyl or fluorinated alkyl group of 1 to 20 carbonatoms. At least one of R¹³ to R¹⁶ should contain —R¹⁷—OR¹¹ or—R¹⁷—CO₂R¹¹. R¹⁷ and R²¹ each are a valence bond or a straight, branchedor cyclic alkylene or fluorinated alkylene group of 1 to 20 carbonatoms. R²² is a straight, branched or cyclic fluorinated alkyl group of1 to 20 carbon atoms.

[0034] R²³ is a methylene group, oxygen atom, sulfur atom or SO₂ R²⁴ toR²⁷ each are a hydrogen atom, fluorine atom, —R²⁸—SO₂F, —R²⁸—SO₃R²⁹ or astraight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 30carbon atoms. At least one of R²⁴ to R²⁷ should contain —R²⁸—SO₂F or—R²⁸—SO₃R²⁹. R²⁸ is a valence bond or a straight, branched or cyclicalkylene or fluorinated alkylene group of 1 to 20 carbon atoms. R²⁹ isan acid labile group, an adhesive group or a straight, branched orcyclic fluorinated alkyl group of 1 to 20 carbon atoms which may containa hydrophilic group such as hydroxyl.

[0035] The subscript “a” is 0 or 1, b is 0 or 1, c is 1 or 2, d is aninteger of 0 to 4, satisfying 1≦c+d≦5, and e is 0 or 1.

[0036] More particularly, suitable straight, branched or cyclic alkylgroups have 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, morepreferably 1 to 10 carbon atoms.

[0037] Examples include, but are not limited to, methyl, ethyl, propyl,isopropyl, n-propyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl,cyclohexyl, cyclohexylmethyl, 2-ethylhexyl, n-octyl, 2-adamantyl, and(2-adamantyl)methyl.

[0038] The fluorinated alkyl groups correspond to the foregoing alkylgroups in which some or all of the hydrogen atoms are replaced byfluorine atoms. Examples include, but are not limited to,trifluoromethyl, 2,2,2-trifluoroethyl, 3,3,3-trifluoropropyl,1,1,1,3,3,3-hexafluoroisopropyl, and 1,1,2,2,3,3,3-heptafluoropropyl aswell as groups of the following formulae.

[0039] Herein, R⁵⁵ is a hydrogen atom, fluorine atom or a straight,branched or cyclic alkyl or fluorinated alkyl group of 1 to 10 carbonatoms, and i is an integer of 0 to 5.

[0040] Suitable straight, branched or cyclic alkylene groups of 1 to 20carbon atoms correspond to the foregoing alkyl groups with one hydrogenatom eliminated. Suitable fluorinated alkylene groups are similaralkylene groups which are partially or entirely substituted withfluorine atoms.

[0041] The acid labile groups represented by R²⁹, R³⁶, R⁴³ and R⁵⁴ areselected from a variety of such groups, preferably from among the groupsof the following formulae (7) to (9).

[0042] In formula (7), R⁵⁶ is a tertiary alkyl group of 4 to 20 carbonatoms, preferably 4 to 15 carbon atoms, or an oxoalkyl group of 4 to 20carbon atoms. Suitable tertiary alkyl groups include tert-butyl,tert-amyl, 1,1-diethylpropyl, 1-ethylcyclopentyl, 1-butylcyclopentyl,1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl,1-ethyl-2-cyclohexenyl, and 2-methyl-2-adamantyl. Suitable oxoalkylgroups include 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, and5-methyl-5-oxooxolan-4-yl. Letter j is an integer of 0 to 6.

[0043] Illustrative, non-limiting, examples of the acid labile group offormula (7) include tert-butoxycarbonyl, tert-butoxycarbonylmethyl,tert-amyloxycarbonyl, tert-amyloxycarbonylmethyl,1,1-diethylpropyloxycarbonyl, 1,1-diethylpropyloxycarbonylmethyl,1-ethylcyclopentyloxycarbonyl, 1-ethylcyclopentyloxycarbonylmethyl,1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl groups.

[0044] In formula (8), R⁵⁷ and R⁵⁸ are hydrogen or straight, branched orcyclic alkyl groups of 1 to 18 carbon atoms, preferably 1 to 10 carbonatoms, for example, methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl andn-octyl. R⁵⁹ is a monovalent hydrocarbon group of 1 to 18 carbon atoms,preferably 1 to 10 carbon atoms, which may contain a hetero atom such asoxygen, for example, straight, branched or cyclic alkyl groups andsubstituted ones of these alkyl groups in which some hydrogen atoms aresubstituted with hydroxyl, alkoxy, oxo, amino or alkylamino groups.Exemplary substituted alkyl groups are shown below.

[0045] A pair of R⁵⁷ and R⁵⁸, a pair of R⁵⁷ and R⁵⁹, or a pair of R⁵⁸and R⁵⁹ may bond together to form a ring. Each of R⁵⁷, R⁵⁸ and R⁵⁹ is astraight or branched alkylene group of 1 to 18 carbon atoms, preferably1 to 10 carbon atoms, when they form a ring.

[0046] Of the acid labile groups of formula (8), straight or branchedones are exemplified by the following groups.

[0047] Of the acid labile groups of formula (8), cyclic ones areexemplified by tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

[0048] Of the groups of formula (8), ethoxyethyl, butoxyethyl andethoxypropyl are preferred.

[0049] In formula (9), R⁶⁰, R⁶¹ and R⁶² each are a monovalenthydrocarbon group, typically a straight, branched or cyclic alkyl groupof 1 to 20 carbon atoms, which may contain a hetero atom such as oxygen,sulfur, nitrogen or fluorine. A pair of R⁶⁰ and R⁶¹, R⁶⁰ and R⁶², andR⁶¹ and R⁶², taken together, may form a ring with the carbon atom towhich they are bonded.

[0050] Examples of the tertiary alkyl group represented by formula (9)include tert-butyl, triethylcarbyl, 1-ethylnorbornyl,1-methylcyclohexyl, 1-ethylcyclopentyl, 2-(2-methyl)adamantyl,2-(2-ethyl)adamantyl, tert-amyl,1,1,1,3,3,3-hexafluoro-2-methyl-isopropyl, and1,1,1,3,3,3-hexafluoro-2-cyclohexyl-isopropyl as well as the groupsshown below.

[0051] Herein, R⁶³ is a straight, branched or cyclic alkyl group of 1 to6 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, n-pentyl, n-hexyl, cyclopropyl, cyclopropylmethyl,cyclobutyl, cyclopentyl and cyclohexyl. R⁶⁴ is a straight, branched orcyclic alkyl group of 2 to 6 carbon atoms, such as ethyl, propyl,isopropyl, n-butyl, sec-butyl, n-pentyl, n-hexyl, cyclopropyl,cyclopropylmethyl, cyclobutyl, cyclopentyl and cyclohexyl. Each of R⁶⁵and R⁶⁶ is hydrogen, a monovalent hydrocarbon group of 1 to 6 carbonatoms which may contain a hetero atom, or a monovalent hydrocarbon groupof 1 to 6 carbon atoms which may be separated by a hetero atom. Thesegroups may be straight, branched or cyclic. The hetero atom is typicallyselected from oxygen, sulfur and nitrogen atoms and may be contained orintervene in the form of —OH, —OR⁶⁷, —O—, —S—, —S(═O)—, —NH₂, —NHR⁶⁷,—N(R⁶⁷)₂, —NH— or —NR⁶⁷— wherein R⁶⁷ is a C₁₋₅ alkyl group. Examples ofR⁶⁵ and R⁶⁶ groups include methyl, hydroxymethyl, ethyl, hydroxyethyl,propyl, isopropyl, n-butyl, sec-butyl, n-pentyl, n-hexyl, methoxy,methoxymethoxy, ethoxy and tert-butoxy.

[0052] Next, the adhesive groups represented by R²⁹, R³⁶ and R⁵⁴ areselected from a variety of such groups, preferably from among the groupsof the following formulae.

[0053] Herein, R⁶⁸ is a methylene group, oxygen atom or sulfur atom.

[0054] In the polymers of the invention, units of at least one typeselected from the recurring units of formulae (4), (4a) and (4b), (5),(5a) and (5b), and (6), shown below, may be incorporated in addition tothe above polymer units of formulae (2a) to (2d) and (3) in order toimprove the dissolution contrast, substrate adhesion and dry etchingresistance of the resist.

[0055] Herein R³⁰ is a methylene group, oxygen atom, sulfur atom or SO₂.R³¹ to R³⁴ each are a hydrogen atom, fluorine atom, —R³⁵—OR³⁶,—R³⁵—CO₂R³⁶ or a straight, branched or cyclic alkyl or fluorinated alkylgroup of 1 to 20 carbon atoms, and at least one of R³¹ to R³⁴ shouldcontain —R³⁵—OR³⁶ or —R³⁵—CO₂R³⁶. R³⁵ is a valence bond or a straight,branched or cyclic alkylene or fluorinated alkylene group of 1 to 20carbon atoms. R³⁶ is a hydrogen atom, an acid labile group, an adhesivegroup or a straight, branched or cyclic fluorinated alkyl group of 1 to20 carbon atoms which may contain a hydrophilic group such as hydroxyl.

[0056] R³⁷ to R⁴⁰ each are a hydrogen atom, fluorine atom or an alkyl orfluorinated alkyl group of 1 to 4 carbon atoms. At least either one ofR³⁷ and R³⁸ contains at least one fluorine atom, and at least either oneof R³⁹ and R⁴⁰ contains at least one fluorine atom.

[0057] R⁴¹ is a hydrogen atom, fluorine atom or a straight, branched orcyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms. R⁴² isa valence bond or a straight, branched or cyclic alkylene or fluorinatedalkylene group of 1 to 20 carbon atoms. R⁴³ is a hydrogen atom or acidlabile group. R⁴⁴ is a fluorine atom or a straight, branched or cyclicfluorinated alkyl group of 1 to 20 carbon atoms.

[0058] R⁴⁵ to R⁵⁰ each are a hydrogen atom, fluorine atom or an alkyl orfluorinated alkyl group of 1 to 4 carbon atoms. At least either one ofR⁴⁵ and R⁴⁶ contains at least one fluorine atom, at least either one ofR⁴⁷ and R⁴⁸ contains at least one fluorine atom, and at least either oneof R⁴⁹ and R⁵⁰ contains at least one fluorine atom.

[0059] R⁵¹ to R⁵³ each are a hydrogen atom, fluorine atom or a straight,branched or cyclic alkyl or fluorinated alkyl group of 1 to 20 carbonatoms. R⁵⁴ is a hydrogen atom, an acid labile group, an adhesive groupor a straight, branched or cyclic fluorinated alkyl group of 1 to 20carbon atoms which may contain a hydrophilic group such as hydroxyl.

[0060] The subscript f is 0 or 1, g is 1 or 2, and h is an integer of 0to 4, satisfying 1≦g+h≦5.

[0061] Illustrative examples of the group of formula (1) are givenbelow, though not limited thereto.

[0062] Herein R⁷ is as defined above.

[0063] Illustrative examples of the polymer units of formulae (2a) to(2d) are given below, though not limited thereto.

[0064] Herein R¹¹ is as defined above.

[0065] Illustrative examples of the polymer units of formula (3) aregiven below, though not limited thereto.

[0066] Herein R²⁹ is as defined above.

[0067] Illustrative examples of the units of formulae (4), (4a) and (4b)are given below, though not limited thereto.

[0068] Herein R³⁶ is as defined above.

[0069] Illustrative examples of the units of formulae (5), (5a) and (5b)are given below, though not limited thereto.

[0070] Herein R⁴³ is as defined above.

[0071] Besides, units as shown below may be incorporated in theinventive polymers for the purpose of improving substrate adhesion andtransparency.

[0072] Herein, R⁶⁹ to R⁷³ each are hydrogen, fluorine or a fluorinatedalkyl group of 1 to 4 carbon atoms, at least one of R⁷⁰ to R⁷³ containsat least one fluorine atom, R⁷⁴ and R⁷⁵ each are hydrogen, methyl ortrifluoromethyl.

[0073] In the inventive polymers wherein U2 represents units of formulae(2a) to (2d), U3 represents units of formula (3), U4 represents units offormulae (4), (4a) and (4b), U5 represents units of formulae (5), (5a)and (5b), U6 represents units of formula (6), and U7 represents adhesiveand transparent units other than the foregoing, and U2 (orU3)+U4+U5+U6+U7=1, U's are preferably in the range:

[0074] 0<U2≦0.6, more preferably 0.1≦U2≦0.4,

[0075] 0<U3≦0.6, more preferably 0.1≦U3≦0.4,

[0076] 0≦U4≦0.6, more preferably 0≦U4≦0.4,

[0077] 0≦U5≦0.6, more preferably 0≦U5≦0.4,

[0078] 0≦U6≦0.7, more preferably 0≦U6≦0.5, and

[0079] 0≦U7≦0.4, more preferably 0≦U7≦0.2.

[0080] The polymers of the invention are generally synthesized bydissolving monomers corresponding to the respective units of formulae(2a) to (2d), (3), (4), (4a), (4b), (5), (5a), (5b) and (6) andoptionally, an adhesion-improving monomer, a transparency-improvingmonomer and the like in a solvent, adding a catalyst thereto, andeffecting polymerization reaction while heating or cooling the system ifnecessary. The polymerization reaction depends on the type of initiatoror catalyst, trigger means (including light, heat, radiation andplasma), and polymerization conditions (including temperature, pressure,concentration, solvent, and additives). Commonly used for preparation ofthe polymers of the invention are radical polymerization of triggeringpolymerization with initiators such as 2,2′-azobisisobutyronitrile(AIBN) or the like, and ion (anion) polymerization using catalysts suchas alkyl lithium. These polymerization steps may be carried out in theirconventional manner.

[0081] The radical polymerization initiator used herein is not critical.Exemplary initiators include azo compounds such as AIBN,2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-azobis(2,4-dimethylvaleronitrile), and2,2′-azobis(2,4,4-trimethylpentane); peroxide compounds such astert-butyl peroxypivalate, lauroyl peroxide, benzoyl peroxide andtert-butyl peroxylaurate; water-soluble initiators, for example,persulfate salts such as potassium persulfate; and redox combinations ofpotassium persulfate or peroxides such as hydrogen peroxide withreducing agents such as sodium sulfite. The amount of the polymerizationinitiator used is determined as appropriate in accordance with suchfactors as the identity of initiator and polymerization conditions,although the amount is often in the range of about 0.001 to 5% byweight, especially about 0.01 to 2% by weight based on the total weightof monomers to be polymerized.

[0082] For the polymerization reaction, a solvent may be used. Thepolymerization solvent used herein is preferably one which does notinterfere with the polymerization reaction. Typical solvents includeester solvents such as ethyl acetate and n-butyl acetate, ketonesolvents such as acetone, methyl ethyl ketone and methyl isobutylketone, aliphatic or aromatic hydrocarbon solvents such as toluene,xylene and cyclohexane, alcohol solvents such as isopropyl alcohol andethylene glycol monomethyl ether, and ether solvents such as diethylether, dioxane, and tetrahydrofuran. These solvents may be used alone orin admixture of two or more. Further, any of well-known molecular weightmodifiers such as dodecylmercaptan may be used in the polymerizationsystem.

[0083] The temperature of polymerization reaction varies in accordancewith the identity of polymerization initiator and the boiling point ofthe solvent although it is often preferably in the range of about 20 to200° C., and especially about 50 to 140° C. Any desired reactor orvessel may be used for the polymerization reaction.

[0084] From the solution or dispersion of the polymer thus obtained, theorganic solvent or water serving as the reaction medium is removed byany of well-known techniques. Suitable techniques include, for example,re-precipitation followed by filtration, and heat distillation undervacuum.

[0085] Desirably the polymer has a weight average molecular weight ofabout 1,000 to about 500,000, and especially about 2,000 to about100,000.

[0086] The polymer of the invention can be used as a base resin inresist compositions, specifically chemical amplification type resistcompositions, and especially chemical amplification type positiveworking resist compositions. It is understood that the polymer of theinvention may be admixed with another polymer for the purpose ofaltering the dynamic properties, thermal properties, alkali solubilityand other physical properties of polymer film. The type of the otherpolymer which can be admixed is not critical. Any of polymers known tobe useful in resist use may be admixed in any desired proportion.

[0087] Resist Composition

[0088] As long as the polymer of the invention is used as a base resin,the resist composition of the invention may be prepared using well-knowncomponents. In a preferred embodiment, the chemically amplified positiveresist composition is defined as comprising (A) the above-definedpolymer as a base resin, (B) an organic solvent, and (C) a photoacidgenerator. In the resist composition, there may be further formulated(D) a basic compound and/or (E) a dissolution inhibitor.

[0089] Component (B)

[0090] The organic solvent used as component (B) in the invention may beany organic solvent in which the base resin (inventive polymer),photoacid generator, and other components are soluble. Illustrative,non-limiting, examples of the organic solvent include ketones such ascyclohexanone and methyl-2-n-amylketone; alcohols such as3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether,ethylene glycol monomethyl ether, propylene glycol monoethyl ether,ethylene glycol monoethyl ether, propylene glycol dimethyl ether, anddiethylene glycol dimethyl ether; esters such as propylene glycolmonomethyl ether acetate, propylene glycol monoethyl ether acetate,ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, and propylene glycol mono-tert-butyl etheracetate; and lactones such as γ-butyrolactone.

[0091] Also useful are fluorinated organic solvents. Illustrative,non-limiting examples include 2-fluoroanisole, 3-fluoroanisole,4-fluoroanisole, 2,3-difluoroanisole, 2,4-difluoroanisole,2,5-difluoroanisole, 5,8-difluoro-1,4-benzodioxane, 2,3-difluorobenzylalcohol, 1,3-difluoro-2-propanol, 2′,4′-difluoropropiophenone,2,4-difluorotoluene, trifluoroacetaldehyde ethyl hemiacetal,trifluoroacetamide, trifluoroethanol, 2,2,2-trifluorobutyrate,ethylheptafluoroethanol, ethyl heptafluorobutylacetate, ethylhexafluoroglutarylmethyl, ethyl 3-hydroxy-4,4,4-trifluoroacetoacetate,ethyl pentafluoropropynylacetate, ethyl perfluorooctanoate, ethyl4,4,4-trifluoroacetoacetate, ethyl 4,4,4-trifluorobutyrate, ethyl4,4,4-trifluorocrotonate, ethyl trifluoropyruvate, sec-ethyltrifluoroacetate, fluorocyclohexane,2,2,3,3,4,4,4-heptafluoro-1-butanol,1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione,1,1,1,3,5,5,5-heptafluoropentane-2,4-dione,3,3,4,4,5,5,5-heptafluoro-2-pentanol,3,3,4,4,5,5,5-heptafluoro-2-pentanone, isopropyl4,4,4-trifluoroacetoacetate, methyl perfluorodecanoate, methylperfluoro(2-methyl-3-oxahexanoate), methyl perfluorononanoate, methylperfluorooctanoate, methyl 2,3,3,3-tetrafluoropropionate, methyltrifluoroacetoacetate, 1,1,1,2,2,6,6,6-octafluoro-2,4-hexanedione,2,2,3,3,4,4,5,5-octafluoro-1-pentanol, 1H,1H,2H,2H-perfluoro-1-decanol,perfluoro-2,5-dimethyl-3,6-dioxane anionic acid methyl ester,2H-perfluoro-5-methyl-3,6-dioxanonane,1H,1H,2H,3H,3H-perfluorononane-1,2-diol, 1H,1H,9H-perfluoro-1-nonanol,1H,1H-perfluorooctanol, 1H,1H,2H,2H-perfluorooctanol,2H-perfluoro-5,8,11,14-tetramethyl-3,6,9,12,15-pentaoxaoctadecane,perfluorotributylamine, perfluorotrihexylamine,perfluoro-2,5,8-trimethyl-3,6,9,12,15-pentaoxaoctadecane, methylperfluoro-2,5,8-trimethyl-3,6,9-trioxadodecanoate,perfluorotripentylamine, perfluorotriisopropylamine,1H,1H,2H,3H,3H-perfluoroundecane-1,2-diol, trifluorobutanol,1,1,1-trifluoro-5-methyl-2,4-hexanedione, 1,1,1-trifluoro-2-propanol,3,3,3-trifluoro-1-propanol, 1,1,1-trifluoro-2-propyl acetate,perfluorobutyltetrahydrofuran, perfluorodecalin,perfluoro(1,2-dimethylcyclohexane), perfluoro(1,3-dimethylcyclohexane),propylene glycol trifluoromethyl ether acetate, propylene glycol methylether trifluoromethyl acetate, butyl trifluoromethylacetate, methyl3-trifluoromethoxypropionate, perfluorocyclohexanone, propylene glycoltrifluoromethyl ether, butyl trifluoroacetate, and1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione.

[0092] These solvents may be used alone or in combinations of two ormore thereof. Of the above organic solvents, preferred are diethyleneglycol dimethyl ether and 1-ethoxy-2-propanol, in which the photoacidgenerator is most soluble, and propylene glycol monomethyl ether acetatewhich is safe, and mixtures thereof.

[0093] The solvent is preferably used in an amount of about 300 to10,000 parts by weight, more preferably about 500 to 5,000 parts byweight per 100 parts by weight of the base resin.

[0094] Component (C)

[0095] The photoacid generator is a compound capable of generating anacid upon exposure to high energy radiation or electron beams andincludes the following:

[0096] (i) onium salts of the formula (P1a-1), (P1a-2) or (P1b),

[0097] (ii) diazomethane derivatives of the formula (P2),

[0098] (iii) glyoxime derivatives of the formula (P3),

[0099] (iv) bissulfone derivatives of the formula (P4),

[0100] (v) sulfonic acid esters of N-hydroxyimide compounds of theformula (P5),

[0101] (vi) β-ketosulfonic acid derivatives,

[0102] (vii) disulfone derivatives,

[0103] (viii) nitrobenzylsulfonate derivatives, and

[0104] (ix) sulfonate derivatives.

[0105] These photoacid generators are described in detail.

[0106] (i) Onium Salts of Formula (P1a-1), (P1a-2) or (P1b):

[0107] Herein, R^(101a), R^(101b), and R^(101c) independently representstraight, branched or cyclic alkyl, alkenyl, oxoalkyl or oxoalkenylgroups of 1 to 12 carbon atoms, aryl groups of 6 to 20 carbon atoms, oraralkyl or aryloxoalkyl groups of 7 to 12 carbon atoms, wherein some orall of the hydrogen atoms may be replaced by alkoxy or other groups.Also, R^(101b) and R^(101c), taken together, may form a ring. R^(101b)and R^(101c) each are alkylene groups of 1 to 6 carbon atoms when theyform a ring. K⁻ is a non-nucleophilic counter ion.

[0108] R^(101a), R^(101b), and R^(101c) may be the same or different andare illustrated below. Exemplary alkyl groups include methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl,heptyl, octyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclopropylmethyl,4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl.Exemplary alkenyl groups include vinyl, allyl, propenyl, butenyl,hexenyl, and cyclohexenyl. Exemplary oxoalkyl groups include2-oxocyclopentyl and 2-oxocyclohexyl as well as 2-oxopropyl,2-cyclopentyl-2-oxoethyl, 2-cyclohexyl-2-oxoethyl, and2-4-ethylcyclohexyl)-2-oxoethyl. Exemplary aryl groups include phenyland naphthyl; alkoxyphenyl groups such as p-ethoxyphenyl,m-methoxyphenyl, o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-ethylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl; alkylnaphthyl groups such asmethylnaphthyl and ethylnaphthyl; alkoxynaphthyl groups such asmethoxynaphthyl and ethoxynaphthyl; dialkylnaphthyl groups such asdimethylnaphthyl and diethylnaphthyl; and dialkoxynaphthyl groups suchas dimethoxynaphthyl and diethoxynaphthyl. Exemplary aralkyl groupsinclude benzyl, phenylethyl, and phenethyl. Exemplary aryloxoalkylgroups are 2-aryl-2-oxoethyl groups such as 2-phenyl-2-oxoethyl,2-1-naphthyl)-2-oxoethyl, and 2-(2-naphthyl)-2-oxoethyl. Examples of thenon-nucleophilic counter ion represented by K⁻ include halide ions suchas chloride and bromide ions, fluoroalkylsulfonate ions such astriflate, 1,1,1-rifluoroethanesulfonate, and nonafluorobutanesulfonate,arylsulfonate ions such as tosylate, benzenesulfonate,4-luorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate, andalkylsulfonate ions such as mesylate and butanesulfonate.

[0109] Herein, R^(102a) and R^(102b) independently represent straight,branched or cyclic alkyl groups of 1 to 8 carbon atoms. R¹⁰³ representsa straight, branched or cyclic alkylene groups of 1 to 10 carbon atoms.R^(104a) and R^(104b) independently represent 2-oxoalkyl groups of 3 to7 carbon atoms. K⁻ is a non-ucleophilic counter ion.

[0110] Illustrative of the groups represented by R^(102a) and R^(102b)are methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,pentyl, hexyl, heptyl, octyl, cyclopentyl, cyclohexyl,cyclopropylmethyl, 4-methylcyclohexyl, and cyclohexylmethyl.Illustrative of the groups represented by R¹⁰³ are methylene, ethylene,propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene,1,4-cyclohexylene, 1,2-cyclohexylene, 1,3-cyclopentylene,1,4-cyclooctylene, and 1,4-cyclohexanedimethylene. Illustrative of thegroups represented by R^(104a) and R^(104b) are 2-oxopropyl,2-oxocyclopentyl, 2-oxocyclohexyl, and 2-oxocycloheptyl. Illustrativeexamples of the counter ion represented by K⁻ are the same asexemplified for formulae (P1a-1) and (P1a-2).

[0111] (ii) Diazomethane Derivatives of Formula (P2)

[0112] Herein, R¹⁰⁵ and R¹⁰⁶ independently represent straight, branchedor cyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms,aryl or halogenated aryl groups of 6 to 20 carbon atoms, or aralkylgroups of 7 to 12 carbon atoms.

[0113] Of the groups represented by R¹⁰⁵ and R¹⁰⁶, exemplary alkylgroups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, pentyl, hexyl, heptyl, octyl, amyl, cyclopentyl, cyclohexyl,cycloheptyl, norbornyl, and adamantyl. Exemplary halogenated alkylgroups include trifluoromethyl, 1,1,1-trifluoroethyl,1,1,1-trichloroethyl, and nonafluorobutyl. Exemplary aryl groups includephenyl; alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl,o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; and alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl. Exemplary halogenated aryl groupsinclude fluorophenyl, chlorophenyl, and 1,2,3,4,5-pentafluorophenyl.Exemplary aralkyl groups include benzyl and phenethyl.

[0114] (iii) Glyoxime Derivatives of Formula (P3)

[0115] Herein, R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ independently represent straight,branched or cyclic alkyl or halogenated alkyl groups of 1 to 12 carbonatoms, aryl or halogenated aryl groups of 6 to 20 carbon atoms, oraralkyl groups of 7 to 12 carbon atoms. Also, R¹⁰⁸ and R¹⁰⁹, takentogether, may form a ring. R¹⁰⁸ and R¹⁰⁹ each are straight or branchedalkylene groups of 1 to 6 carbon atoms when they form a ring.

[0116] Illustrative examples of the alkyl, halogenated alkyl, aryl,halogenated aryl, and aralkyl groups represented by R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹are the same as exemplified for R¹⁰⁵ and R¹⁰⁶ Examples of the alkylenegroups represented by R¹⁰⁸ and R¹⁰⁹ include methylene, ethylene,propylene, butylene, and hexylene.

[0117] (iv) Bissulfone Derivatives of Formula (P4)

[0118] Herein, R^(101a) and R^(101b) are as defined above.

[0119] (v) Sulfonic Acid Esters of N-Hydroxyimide Compounds of Formula(P5)

[0120] Herein, R¹¹⁰ is an arylene group of 6 to 10 carbon atoms,alkylene group of 1 to 6 carbon atoms, or alkenylene group of 2 to 6carbon atoms wherein some or all of the hydrogen atoms may be replacedby straight or branched alkyl or alkoxy groups of 1 to 4 carbon atoms,nitro, acetyl, or phenyl groups. R¹¹¹ is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms, alkenyl, alkoxyalkyl, phenyl ornaphthyl group wherein some or all of the hydrogen atoms may be replacedby alkyl or alkoxy groups of 1 to 4 carbon atoms, phenyl groups (whichmay have substituted thereon an alkyl or alkoxy of 1 to 4 carbon atoms,nitro, or acetyl group), hetero-aromatic groups of 3 to 5 carbon atoms,or chlorine or fluorine atoms.

[0121] Of the groups represented by R¹¹⁰, exemplary arylene groupsinclude 1,2-phenylene and 1,8-naphthylene; exemplary alkylene groupsinclude methylene, ethylene, trimethylene, tetramethylene,phenylethylene, and norbornane-2,3-diyl; and exemplary alkenylene groupsinclude 1,2-vinylene, 1-phenyl-1,2-vinylene, and 5-norbornene-2,3-diyl.Of the groups represented by R¹¹¹, exemplary alkyl groups are asexemplified for R^(101a) to R^(101c); exemplary alkenyl groups includevinyl, 1-propenyl, allyl, 1-butenyl, 3-butenyl, isoprenyl, 1-pentenyl,3-pentenyl, 4-pentenyl, dimethylallyl, 1-hexenyl, 3-hexenyl, 5-hexenyl,1-heptenyl, 3-heptenyl, 6-heptenyl, and 7-octenyl; and exemplaryalkoxyalkyl groups include methoxymethyl, ethoxymethyl, propoxymethyl,butoxymethyl, pentyloxymethyl, hexyloxymethyl, heptyloxymethyl,methoxyethyl, ethoxyethyl, propoxyethyl, butoxyethyl, pentyloxyethyl,hexyloxyethyl, methoxypropyl, ethoxypropyl, propoxypropyl, butoxypropyl,methoxybutyl, ethoxybutyl, propoxybutyl, methoxypentyl, ethoxypentyl,methoxyhexyl, and methoxyheptyl.

[0122] Of the substituents on these groups, the alkyl groups of 1 to 4carbon atoms include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyland tert-butyl; the alkoxy groups of 1 to 4 carbon atoms includemethoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, andtert-butoxy; the phenyl groups which may have substituted thereon analkyl or alkoxy of 1 to 4 carbon atoms, nitro, or acetyl group includephenyl, tolyl, p-tert-butoxyphenyl, p-acetylphenyl and p-nitrophenyl;the hetero-aromatic groups of 3 to 5 carbon atoms include pyridyl andfuryl.

[0123] Illustrative examples of the photoacid generator include:

[0124] onium salts such as diphenyliodonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)phenyliodonium trifluoromethanesulfonate,diphenyliodonium p-toluenesulfonate, (p-tert-butoxyphenyl)phenyliodoniump-toluenesulfonate, triphenylsulfonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,bis(p-tert-butoxyphenyl)phenylsulfonium trifluoromethanesulfonate,tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,triphenylsulfonium p-toluenesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,bis(p-tert-butoxyphenyl)phenylsulfonium p-toluenesulfonate,tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,triphenylsulfonium nonafluorobutanesulfonate, triphenylsulfoniumbutanesulfonate, trimethylsulfonium trifluoromethanesulfonate,trimethylsulfonium p-toluenesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium p-toluenesulfonate,dimethylphenylsulfonium trifluoromethanesulfonate,dimethylphenylsulfonium p-toluenesulfonate, dicyclohexylphenylsulfoniumtrifluoromethanesulfonate, dicyclohexylphenylsulfoniump-toluenesulfonate, trinaphthylsulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,(2-norbornyl)methyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,ethylenebis-[methyl(2-oxocyclopentyl)sulfoniumtrifluoromethanesulfonate], and1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;

[0125] diazomethane derivatives such asbis(benzenesulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(xylenesulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane,bis(cyclopentylsulfonyl)diazomethane, bis(n-butylsulfonyl)diazomethane,bis(isobutylsulfonyl)diazomethane, bis(sec-butylsulfonyl)diazomethane,bis(n-propylsulfonyl)diazomethane, bis(isopropylsulfonyl)diazomethane,bis(tert-butylsulfonyl)diazomethane, bis(n-amylsulfonyl)diazomethane,bis(isoamylsulfonyl)diazomethane, bis(sec-amylsulfonyl)diazomethane,bis(tert-amylsulfonyl)diazomethane,1-cyclohexylsulfonyl-1-(tert-butylsulfonyl)diazomethane,1-cyclohexylsulfonyl-1-(tert-amylsulfonyl)diazomethane, and1-tert-amylsulfonyl-1-(tert-butylsulfonyl)diazomethane;

[0126] glyoxime derivatives such asbis-O-(p-toluenesulfonyl)-α-dimethylglyoxime,bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime,bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-O-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-O-(n-butanesulfonyl)-α-dimethylglyoxime,bis-O-(n-butanesulfonyl)-α-diphenylglyoxime,bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime,bis-O-(n-butanesulfonyl)-2,3-pentanedioneglyoxime,bis-O-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-O-(methanesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime,bis-O-(1,1,1-trifluoroethanesulfonyl)-α-dimethylglyoxime,bis-O-(tert-butanesulfonyl)-α-dimethylglyoxime,bis-O-(perfluorooctanesulfonyl)-α-dimethylglyoxime,bis-O-(cyclohexanesulfonyl)-α-dimethylglyoxime,bis-O-(benzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-tert-butylbenzenesulfonyl)-α-dimethylglyoxime,bis-O-(xylenesulfonyl)-α-dimethylglyoxime, andbis-O-(camphorsulfonyl)-α-dimethylglyoxime;

[0127] bissulfone derivatives such as bisnaphthylsulfonylmethane,bistrifluoromethylsulfonylmethane, bismethylsulfonylmethane,bisethylsulfonylmethane, bispropylsulfonylmethane,bisisopropylsulfonylmethane, bis-p-toluenesulfonylmethane, andbisbenzenesulfonylmethane;

[0128] β-ketosulfone derivatives such as2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane and2-isopropylcarbonyl-2-(p-toluenesulfonyl)propane;

[0129] nitrobenzyl sulfonate derivatives such as 2,6-dinitrobenzylp-toluenesulfonate and 2,4-dinitrobenzyl p-toluenesulfonate;

[0130] sulfonic acid ester derivatives such as1,2,3-tris(methanesulfonyloxy)benzene,1,2,3-tris(trifluoromethanesulfonyloxy)benzene, and1,2,3-tris(p-toluenesulfonyloxy)benzene; and

[0131] sulfonic acid esters of N-hydroxyimides such asN-hydroxysuccinimide methanesulfonate, N-hydroxysuccinimidetrifluoromethanesulfonate, N-hydroxysuccinimide ethanesulfonate,N-hydroxysuccinimide 1-propanesulfonate, N-hydroxysuccinimide2-propanesulfonate, N-hydroxysuccinimide 1-pentanesulfonate,N-hydroxysuccinimide 1-octanesulfonate, N-hydroxysuccinimidep-toluenesulfonate, N-hydroxysuccinimide p-methoxybenzenesulfonate,N-hydroxysuccinimide 2-chloroethanesulfonate, N-hydroxysuccinimidebenzenesulfonate, N-hydroxysuccinimide 2,4,6-trimethylbenzenesulfonate,N-hydroxysuccinimide 1-naphthalenesulfonate, N-hydroxysuccinimide2-naphthalenesulfonate, N-hydroxy-2-phenylsuccinimide methanesulfonate,N-hydroxymaleimide methanesulfonate, N-hydroxymaleimide ethanesulfonate,N-hydroxy-2-phenylmaleimide methanesulfonate, N-hydroxyglutarimidemethanesulfonate, N-hydroxyglutarimide benzenesulfonate,N-hydroxyphthalimide methanesulfonate, N-hydroxyphthalimidebenzenesulfonate, N-hydroxyphthalimide trifluoromethanesulfonate,N-hydroxyphthalimide p-toluenesulfonate, N-hydroxynaphthalimidemethanesulfonate, N-hydroxynaphthalimide benzenesulfonate,N-hydroxy-5-norbornene-2,3-dicarboxyimide methanesulfonate,N-hydroxy-5-norbornene-2,3-dicarboxyimide trifluoromethanesulfonate, andN-hydroxy-5-norbornene-2,3-dicarboxyimide p-toluenesulfonate.

[0132] Preferred among these photoacid generators are onium salts suchas triphenylsulfonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,triphenylsulfonium p-toluenesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,trinaphthylsulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,(2-norbornyl)methyl(2-oxocylohexyl)sulfonium trifluoromethanesulfonate,and 1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;diazomethane derivatives such as bis(benzenesulfonyl)diazomethane,bis(p-toluenesulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane,bis(n-butylsulfonyl)diazomethane, bis(isobutylsulfonyl)diazomethane,bis(sec-butylsulfonyl)diazomethane, bis(n-propylsulfonyl)diazomethane,bis(isopropylsulfonyl)diazomethane, andbis(tert-butylsulfonyl)diazomethane; glyoxime derivatives such asbis-O-(p-toluenesulfonyl)-α-dimethylglyoxime andbis-O-(n-butanesulfonyl)-α-dimethylglyoxime; bissulfone derivatives suchas bisnaphthylsulfonylmethane; and sulfonic acid esters ofN-hydroxyimide compounds such as N-hydroxysuccinimide methanesulfonate,N-hydroxysuccinimide trifluoromethanesulfonate, N-hydroxysuccinimide1-propanesulfonate, N-hydroxysuccinimide 2-propanesulfonate,N-hydroxysuccinimide 1-pentanesulfonate, N-hydroxysuccinimidep-toluenesulfonate, N-hydroxynaphthalimide methanesulfonate, andN-hydroxynaphthalimide benzenesulfonate.

[0133] These photoacid generators may be used singly or in combinationsof two or more thereof. Onium salts are effective for improvingrectangularity, while diazomethane derivatives and glyoxime derivativesare effective for reducing standing waves. The combination of an oniumsalt with a diazomethane or a glyoxime derivative allows for fineadjustment of the profile.

[0134] The photoacid generator is added in an amount of 0.1 to 50 parts,and especially 0.5 to 40 parts by weight, per 100 parts by weight of thebase resin (all parts are by weight, hereinafter). Less than 0.1 part ofthe photoacid generator may generate a less amount of acid uponexposure, sometimes leading to a poor sensitivity and resolution whereasmore than 50 parts of the photoacid generator may adversely affecttransparency and resolution.

[0135] Component (D)

[0136] The basic compound used as component (D) is preferably a compoundcapable of suppressing the rate of diffusion when the acid generated bythe photoacid generator diffuses within the resist film. The inclusionof this type of basic compound holds down the rate of acid diffusionwithin the resist film, resulting in better resolution. In addition, itsuppresses changes in sensitivity following exposure, thus reducingsubstrate and environment dependence, as well as improving the exposurelatitude and the pattern profile.

[0137] Examples of suitable basic compounds include primary, secondary,and tertiary aliphatic amines, mixed amines, aromatic amines,heterocyclic amines, carboxyl group-bearing nitrogenous compounds,sulfonyl group-bearing nitrogenous compounds, hydroxyl group-bearingnitrogenous compounds, hydroxyphenyl group-bearing nitrogenouscompounds, alcoholic nitrogenous compounds, amide derivatives, and imidederivatives.

[0138] Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,iso-butylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine,di-iso-propylamine, di-n-butylamine, di-iso-butylamine,di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine,dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine,didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, tri-iso-propylamine, tri-n-butylamine,tri-iso-butylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

[0139] Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic amines includeaniline derivatives (e.g., aniline, N-methylaniline, N-ethylaniline,N-propylaniline, N,N-dimethylaniline, 2-methylaniline, 3-methylaniline,4-ethylaniline, ethylaniline, propylaniline, trimethylaniline,2-nitroaniline, 3-nitroaniline, 4-nitroaniline, 2,4-initroaniline,2,6-dinitroaniline, 3,5-dinitroaniline, and N,N-dimethyltoluidine),diphenyl(p-tolyl)amine, methyldiphenylamine, triphenylamine,phenylenediamine, naphthylamine, and diaminonaphthalene. Examples ofsuitable heterocyclic amines include pyrrole derivatives (e.g., pyrrole,2H-pyrrole, 1-methylpyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole,and N-methylpyrrole), oxazole derivatives (e.g., oxazole andisooxazole), thiazole derivatives (e.g., thiazole and isothiazole),imidazole derivatives (e.g., imidazole, 4-methylimidazole, and4-methyl-2-phenylimidazole), pyrazole derivatives, furazan derivatives,pyrroline derivatives (e.g., pyrroline and 2-methyl-1-pyrroline),pyrrolidine derivatives (e.g., pyrrolidine, N-methylpyrrolidine,pyrrolidinone, and N-methylpyrrolidone), imidazoline derivatives,imidazolidine derivatives, pyridine derivatives (e.g., pyridine,methylpyridine, ethylpyridine, propylpyridine, butylpyridine,4-(1-butylpentyl)pyridine, dimethylpyridine, trimethylpyridine,triethylpyridine, phenylpyridine, 3-methyl-2-phenylpyridine,4-tert-butylpyridine, diphenylpyridine, benzylpyridine, methoxypyridine,butoxypyridine, dimethoxypyridine, 1-methyl-2-pyridine,4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine,2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine),pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives,pyrazoline derivatives, pyrazolidine derivatives, piperidinederivatives, piperazine derivatives, morpholine derivatives, indolederivatives, isoindole derivatives, 1H-indazole derivatives, indolinederivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

[0140] Examples of suitable carboxyl group-bearing nitrogenous compoundsinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g., nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine).

[0141] Examples of suitable sulfonyl group-bearing nitrogenous compoundsinclude 3-pyridinesulfonic acid and pyridinium p-toluenesulfonate.

[0142] Examples of suitable hydroxyl group-bearing nitrogenouscompounds, hydroxyphenyl group-bearing nitrogenous compounds, andalcoholic nitrogenous compounds include 2-hydroxypyridine, aminocresol,2,4-quinolinediol, 3-indolemethanol hydrate, monoethanolamine,diethanolamine, triethanolamine, N-ethyldiethanolamine,N,N-diethylethanolamine, triisopropanolamine, 2,2′-iminodiethanol,2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butanol,4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine,1-(2-hydroxyethyl)piperazine, 1-[2-(2-hydroxyethoxy)ethyl]-piperazine,piperidine ethanol, 1-(2-hydroxyethyl)pyrrolidine,1-(2-hydroxyethyl)-2-pyrrolidinone, 3-piperidino-1,2-propanediol,3-pyrrolidino-1,2-propanediol, 8-hydroxyjulolidine, 3-quinuclidinol,3-tropanol, 1-methyl-2-pyrrolidine ethanol, 1-aziridine ethanol,N-(2-hydroxyethyl)phthalimide, and N-(2-hydroxyethyl)isonicotinamide.

[0143] Examples of suitable amide derivatives include formamide,N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide,N,N-dimethylacetamide, propionamide, and benzamide. Suitable imidederivatives include phthalimide, succinimide, and maleimide.

[0144] In addition, basic compounds of the following general formula(B)-1 may also be included alone or in admixture.

[0145] In the formulas, n is 1, 2 or 3. The side chain X may be the sameor different and is represented by the formula (X)-1, (X)-2 or (X)-3.The side chain Y may be the same or different and stands for hydrogen ora straight, branched or cyclic alkyl group of 1 to 20 carbon atoms whichmay contain an ether or hydroxyl group. Two or three X's may bondtogether to form a ring.

—R³⁰⁰—O—R³⁰¹  (X)-1

[0146] In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straightor branched alkylene groups of 1 to 4 carbon atoms; R³⁰¹ and R³⁰⁴ areindependently hydrogen, straight, branched or cyclic alkyl groups of 1to 20 carbon atoms, which may contain at least one hydroxyl group,ether, ester or lactone ring; and R³⁰³ is a single bond or a straight orbranched alkylene group of 1 to 4 carbon atoms; and R³⁰⁶ is a straight,branched or cyclic alkyl group of 1 to 20 carbon atoms, which maycontain at least one hydroxyl group, ether, ester or lactone ring.

[0147] Illustrative, non-limiting examples of the compounds of formula(B)-1 include tris(2-methoxymethoxyethyl)amine,tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane,1-aza-12-crown-4,1-aza-15-crown-5,1-aza-18-crown-6,tris(2-formyloxyethyl)amine, tris(2-acetoxyethyl)amine,tris(2-propionyloxyethyl)amine, tris(2-butyryloxyethyl)amine,tris(2-isobutyryloxyethyl)amine, tris(2-valeryloxyethyl)amine,tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]-amine,tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)-methoxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine,N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxyethyl)amine,N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andβ-(diethylamino)-δ-valerolactone.

[0148] Also useful are one or more of cyclic structure-bearing basiccompounds having the following general formula (B)-2.

[0149] Herein X is as defined above, and R³⁰⁷ is a straight or branchedalkylene group of 2 to 20 carbon atoms which may contain one or morecarbonyl, ether, ester or sulfide groups.

[0150] Illustrative examples of the cyclic structure-bearing basiccompounds having formula (B)-2 include1-[2-(methoxymethoxy)ethyl]pyrrolidine,1-[2-(methoxymethoxy)ethyl]-piperidine,4-[2-(methoxymethoxy)ethyl]morpholine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine,4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine, 2-(1-pyrrolidinyl)ethylacetate, 2-piperidinoethyl acetate, 2-morpholinoethyl acetate,2-(1-pyrrolidinyl)ethyl formate, 2-piperidinoethyl propionate,2-morpholinoethyl acetoxyacetate, 2-(1-pyrrolidinyl)ethylmethoxyacetate, 4-[2-(methoxycarbonyloxy)ethyl]morpholine,1-[2-(t-butoxycarbonyloxy)ethyl]piperidine,4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine, methyl3-(1-pyrrolidinyl)propionate, methyl 3-piperidinopropionate, methyl3-morpholinopropionate, methyl 3-(thiomorpholino)propionate, methyl2-methyl-3-(1-pyrrolidinyl)propionate, ethyl 3-morpholinopropionate,methoxycarbonylmethyl 3-piperidinopropionate, 2-hydroxyethyl3-(1-pyrrolidinyl)propionate, 2-acetoxyethyl 3-morpholinopropionate,2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate,tetrahydrofurfuryl 3-morpholinopropionate, glycidyl3-piperidinopropionate, 2-methoxyethyl 3-morpholinopropionate,2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate, butyl3-morpholinopropionate, cyclohexyl 3-piperidinopropionate,α-(1-pyrrolidinyl)methyl-y-butyrolactone, β-piperidino-γ-butyrolactone,β-morpholino-δ-valerolactone, methyl 1-pyrrolidinylacetate, methylpiperidinoacetate, methyl morpholinoacetate, methylthiomorpholinoacetate, ethyl 1-pyrrolidinylacetate, and 2-methoxyethylmorpholinoacetate.

[0151] Also, one or more of cyano-bearing basic compounds having thefollowing general formulae (B)-3 to (B)-6 may be blended.

[0152] Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹each are independently a straight or branched alkylene group of 1 to 4carbon atoms.

[0153] Illustrative examples of the cyano-bearing basic compoundsinclude 3-(diethylamino)propiononitrile,N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile,N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile,N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile,N,N-bis(2-methoxyethyl)-3-aminopropiononitrile,N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, methylN-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate, methylN-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate,N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile,N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile,N-(3-acetoxy-1-propyl) —N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile,N,N-bis(2-cyanoethyl)-3-aminopropiononitrile, diethylaminoacetonitrile,N,N-bis(2-hydroxyethyl)aminoacetonitrile,N,N-bis(2-acetoxyethyl)aminoacetonitrile,N,N-bis(2-formyloxyethyl)aminoacetonitrile,N,N-bis(2-methoxyethyl)aminoacetonitrile,N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile, methylN-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate, methylN-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate,N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile, N-(2-acetoxyethyl)—N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile,N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile,N-cyanomethyl-N-[2-(methoxymethoxy)ethyl]aminoacetonitrile,N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile,N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile,N,N-bis(cyanomethyl)aminoacetonitrile, 1-pyrrolidinepropiononitrile,1-piperidinepropiononitrile, 4-morpholinepropiononitrile,1-pyrrolidineacetonitrile, 1-piperidineacetonitrile,4-morpholineacetonitrile, cyanomethyl 3-diethylaminopropionate,cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-methoxyethyl)-3-aminopropionate, cyanomethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, 2-cyanoethyl3-diethylaminopropionate, 2-cyanoethylN,N-bis(2-hydroxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-methoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, cyanomethyl1-pyrrolidinepropionate, cyanomethyl 1-piperidinepropionate, cyanomethyl4-morpholinepropionate, 2-cyanoethyl 1-pyrrolidinepropionate,2-cyanoethyl 1-piperidinepropionate, and 2-cyanoethyl4-morpholinepropionate.

[0154] These basic compounds may be used alone or in admixture of any.The basic compound is preferably formulated in an amount of 0.001 to 2parts, and especially 0.01 to 1 part by weight, per 100 parts by weightof the base resin. Less than 0.001 part of the basic compound may failto achieve the desired effects thereof, while the use of more than 2parts would result in too low a sensitivity.

[0155] Component (E)

[0156] The dissolution inhibitor (E) is preferably selected fromcompounds possessing a weight average molecular weight of 100 to 1,000and having on the molecule at least two phenolic hydroxyl groups, inwhich an average of from 10 to 100 mol % of all the hydrogen atoms onthe phenolic hydroxyl groups are replaced with acid labile groups.

[0157] Illustrative, non-limiting, examples of the dissolution inhibitor(E) which are useful herein includebis(4-(2′-tetrahydropyranyloxy)phenyl)methane,bis(4-(2′-tetrahydrofuranyloxy)phenyl)methane,bis(4-tert-butoxyphenyl)methane,bis(4-tert-butoxycarbonyloxyphenyl)methane,bis(4-tert-butoxycarbonylmethyloxyphenyl)methane,bis(4-(1′-ethoxyethoxy)phenyl)methane,bis(4-(1′-ethoxypropyloxy)phenyl)methane,2,2-bis(4′-(2″-tetrahydropyranyloxy))propane,2,2-bis(4′-(2″-tetrahydrofuranyloxy)phenyl)propane,2,2-bis(4′-tert-butoxyphenyl)propane,2,2-bis(4′-tert-butoxycarbonyloxyphenyl)propane,2,2-bis(4-tert-butoxycarbonylmethyloxyphenyl)propane,2,2-bis(4′-(1″-ethoxyethoxy)phenyl)propane,2,2-bis(4′-(1″-ethoxypropyloxy)phenyl)propane, tert-butyl4,4-bis(4′-(2″-tetrahydropyranyloxy)phenyl)valerate, tert-butyl4,4-bis(4′-(2″-tetrahydrofuranyloxy)phenyl)valerate, tert-butyl4,4-bis(4′-tert-butoxyphenyl)valerate, tert-butyl4,4-bis(4-tert-butoxycarbonyloxyphenyl)valerate, tert-butyl4,4-bis(4′-tert-butoxycarbonylmethyloxyphenyl)valerate, tert-butyl4,4-bis(4′-(1″-ethoxyethoxy)phenyl)valerate, tert-butyl4,4-bis(4′-(1″-ethoxypropyloxy)phenyl)valerate,tris(4-(2′-tetrahydropyranyloxy)phenyl)methane,tris(4-(2′-tetrahydrofuranyloxy)phenyl)methane,tris(4-tert-butoxyphenyl)methane,tris(4-tert-butoxycarbonyloxyphenyl)methane,tris(4-tert-butoxycarbonyloxymethylphenyl)methane,tris(4-(1′-ethoxyethoxy)phenyl)methane,tris(4-(1′-ethoxypropyloxy)phenyl)methane,1,1,2-tris(4′-(2″-tetrahydropyranyloxy)phenyl)ethane,1,1,2-tris(4′-(2″-tetrahydrofuranyloxy)phenyl)ethane,1,1,2-tris(4′-tert-butoxyphenyl)ethane,1,1,2-tris(4′-tert-butoxycarbonyloxyphenyl)ethane,1,1,2-tris(4′-tert-butoxycarbonylmethyloxyphenyl)ethane,1,1,2-tris(4′-(1′-ethoxyethoxy)phenyl)ethane, and1,1,2-tris(4′-(1′-ethoxypropyloxy)phenyl)ethane.

[0158] The compounds serving as dissolution inhibitor have a weightaverage molecular weight of 100 to 1,000, preferably 150 to 800. Anappropriate amount of the dissolution inhibitor (E) is 0 to about 50parts, preferably about 5 to 50 parts, and especially about 10 to 30parts by weight per 100 parts by weight of the base resin. Less amountsof the dissolution inhibitor may fail to yield an improved resolution,whereas too much amounts would lead to slimming of the patterned film,and thus a decline in resolution. The inhibitor may be used singly or asa mixture of two or more thereof.

[0159] The resist composition of the invention may include optionalingredients, typically a surfactant which is commonly used for improvingthe coating characteristics. Optional ingredients may be added inconventional amounts so long as this does not compromise the objects ofthe invention.

[0160] Illustrative, non-limiting, examples of the surfactant includenonionic surfactants, for example, polyoxyethylene alkyl ethers such aspolyoxyethylene lauryl ether, polyoxyethylene stearyl ether,polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether,polyoxyethylene alkylaryl ethers such as polyoxyethylene octylphenolether and polyoxyethylene nonylphenol ether, polyoxyethylenepolyoxypropylene block copolymers, sorbitan fatty acid esters such assorbitan monolaurate, sorbitan monopalmitate, and sorbitan monostearate,and polyoxyethylene sorbitan fatty acid esters such as polyoxyethylenesorbitan monolaurate, polyoxyethylene sorbitan monopalmitate,polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitantrioleate, and polyoxyethylene sorbitan tristearate; fluorochemicalsurfactants such as EFTOP EF301, EF303 and EF352 (Tohkem Products Co.,Ltd.), Megaface F171, F172 and F173 (Dai-Nippon Ink & Chemicals, Inc.),Florade FC430 and FC431 (Sumitomo 3M Co., Ltd.), Asahiguard AG710,Surflon S-381, S-382, SC101, SC102, SC103, SC104, SC105, SC106, SurfynolE1004, KH-10, KH-20, KH-30 and KH-40 (Asahi Glass Co., Ltd.);organosiloxane polymers KP341, X-70-092 and X-70-093 (Shin-Etsu ChemicalCo., Ltd.), acrylic acid or methacrylic acid Polyflow No. 75 and No. 95(Kyoeisha Ushi Kagaku Kogyo Co., Ltd.). Inter alia, FC430, SurflonS-381, Surfynol E1004, KH-20 and KH-30 are preferred. These surfactantsmay be used alone or in admixture.

[0161] Pattern formation using the resist composition of the inventionmay be carried out by a known lithographic technique. For example, theresist composition may be applied onto a substrate such as a siliconwafer by spin coating or the like to form a resist film having athickness of 0.1 to 1.0 μm, which is then pre-baked on a hot plate at 60to 200° C. for 10 seconds to 10 minutes, and preferably at 80 to 150° C.for ½ to 5 minutes. A patterning mask having the desired pattern maythen be placed over the resist film, and the film exposed through themask to an electron beam or to high-energy radiation such as deep-UVrays, excimer laser beams, or x-rays in a dose of about 1 to 200 mJ/cm²,and preferably about 10 to 100 mJ/cm², then post-exposure baked (PEB) ona hot plate at 60 to 150° C. for 10 seconds to 5 minutes, and preferablyat 80 to 130° C. for ½ to 3 minutes. Finally, development may be carriedout using as the developer an aqueous alkali solution, such as 0.1 to5%, and preferably 2 to 3%, tetramethylammonium hydroxide (TMAH), thisbeing done by a conventional method such as dipping, puddling, orspraying for a period of 10 seconds to 3 minutes, and preferably 30seconds to 2 minutes. These steps result in the formation of the desiredpattern on the substrate.

[0162] Of the various types of high-energy radiation that may be used,the resist composition of the invention is best suited to micro-patternformation with, in particular, deep-UV rays having a wavelength of 254to 120 nm, an excimer laser, especially ArF excimer laser (193 nm), F₂excimer laser (157 nm), Kr₂ excimer laser (146 nm), KrAr excimer laser(134 nm) or Ar₂ excimer laser (126 nm), x-rays, or an electron beam.Recommended is exposure to high-energy radiation in a wavelength band of100 to 180 nm or 1 to 30 nm, specifically F₂ laser beam, Ar₂ laser beamor soft x-ray. The desired pattern may not be obtainable outside theupper and lower limits of the above range.

[0163] The resist composition of the invention is sensitive tohigh-energy radiation, maintains transparency at a wavelength of up to200 nm, and exhibits a high alkali dissolution contrast and plasmaetching resistance. These features of the inventive resist compositionpermit a finely defined pattern having a high aspect ratio and sidewallsperpendicular to the substrate to be easily formed through F₂ laserexposure, making the resist ideal as a micropatterning material in VLSIfabrication.

EXAMPLE

[0164] Examples of the invention are given below by way of illustrationand not by way of limitation. The abbreviations used herein are AIBN forazobisisobutyronitrile, GPC for gel permeation chromatography, NMR fornuclear magnetic resonance, Mw for weight average molecular weight, andMn for number average molecular weight. Mw/Mn is a molecular weightdistribution or dispersity.

Synthesis Example 1

[0165] Copolymerization of Monomer 1, Monomer 2 and tert-butylα-trifluoromethylacrylate (30:30:40)

[0166] A 300-ml flask was charged with 9.29 g of Monomer 1, 5.48 g ofMonomer 2, both shown below, and 5.23 g of tert-butylα-trifluoromethylacrylate, which were dissolved in 8.6 g of toluene. Thesystem was fully purged of oxygen, charged with 0.22 g of the initiatorAIBN, and heated at 60° C. at which polymerization reaction took placefor 24 hours.

[0167] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in tetrahydrofuran (THF) and pouring in 3 litersof hexane for precipitation was repeated twice, after which the polymerwas separated and dried. There was obtained 14.5 g of a white polymer,which was found to have a Mw of 6,400 as measured by the lightscattering method, and a dispersity (Mw/Mn) of 1.5 as determined fromthe GPC elution curve. On ¹H-NMR analysis, the polymer was found toconsist of Monomer 1, Monomer 2 and tert-butyl α-trifluoromethylacrylatein a molar ratio of 28:31:41.

Synthesis Example 2

[0168] Copolymerization of Monomer 1, Monomer 2 and 2-methyladamantylα-trifluoromethylacrylate (30:30:40)

[0169] A 300-ml flask was charged with 8.27 g of Monomer 1, 4.88 g ofMonomer 2, and 6.85 g of 2-methyladamantyl α-trifluoromethylacrylate,which were dissolved in 8.6 g of toluene. The system was fully purged ofoxygen, charged with 0.20 g of the initiator AIBN, and heated at 60° C.at which polymerization reaction took place for 24 hours.

[0170] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 3 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 15.4 g of a white polymer, which was foundto have a Mw of 6,200 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.5 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 1, Monomer2 and 2-methyladamantyl α-trifluoromethylacrylate in a molar ratio of31:31:38.

Synthesis Example 3

[0171] Copolymerization of Monomer 3, Monomer 2 and tert-butylα-trifluoromethylacrylate (30:30:40)

[0172] A 300-ml flask was charged with 7.42 g of Monomer 3, shown below,6.44 g of Monomer 2, and 6.14 g of tert-butyl α-trifluoromethylacrylate,which were dissolved in 8.6 g of toluene. The system was fully purged ofoxygen, charged with 0.26 g of the initiator AIBN, and heated at 60° C.at which polymerization reaction took place for 24 hours.

[0173] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 3 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 14.4 g of a white polymer, which was foundto have a Mw of 7,300 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.5 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 3, Monomer2 and tert-butyl α-trifluoromethylacrylate in a molar ratio of 28:31:41.

Synthesis Example 4

[0174] Copolymerization of Monomer 3, Monomer 2 and 2-methyladamantylα-trifluoromethylacrylate (30:30:40)

[0175] A 300-ml flask was charged with 6.49 g of Monomer 3, 5.63 g ofMonomer 2, and 7.89 g of 2-methyladamantyl α-trifluoromethylacrylate,which were dissolved in 8.6 g of toluene. The system was fully purged ofoxygen, charged with 0.23 g of the initiator AIBN, and heated at 60° C.at which polymerization reaction took place for 24 hours.

[0176] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 3 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 14.5 g of a white polymer, which was foundto have a Mw of 6,800 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.5 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 3, Monomer2 and 2-methyladamantyl α-trifluoromethylacrylate in a molar ratio of31:31:38.

Synthesis Example 5

[0177] Copolymerization of Monomer 1, Monomer 4 and 2-methyladamantylα-trifluoromethylacrylate (10:50:40)

[0178] A 300-ml flask was charged with 3.13 g of Monomer 1, 9.10 g ofMonomer 4, shown below, and 7.77 g of 2-methyladamantylα-trifluoromethylacrylate, which were dissolved in 8.6 g of toluene. Thesystem was fully purged of oxygen, charged with 0.22 g of the initiatorAIBN, and heated at 60° C. at which polymerization reaction took placefor 24 hours.

[0179] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 3 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 14.4 g of a white polymer, which was foundto have a Mw of 7,100 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.5 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 1, Monomer4 and 2-methyladamantyl α-trifluoromethylacrylate in a molar ratio of12:51:37.

Synthesis Example 6

[0180] Copolymerization of Monomer 3, Monomer 4 and 2-methyladamantylα-trifluoromethylacrylate (10:50:40)

[0181] A 300-ml flask was charged with 2.24 g of Monomer 3, 9.58 g ofMonomer 4, and 8.18 g of 2-methyladamantyl α-trifluoromethylacrylate,which were dissolved in 8.6 g of toluene. The system was fully purged ofoxygen, charged with 0.23 g of the initiator AIBN, and heated at 60° C.at which polymerization reaction took place for 24 hours.

[0182] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 3 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 14.1 g of a white polymer, which was foundto have a Mw of 7,200 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.5 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 3, Monomer4 and 2-methyladamantyl α-trifluoromethylacrylate in a molar ratio of13:51:38.

Synthesis Example 7

[0183] Copolymerization of Monomer 5 and tert-butylα-trifluoromethylacrylate (6:4)

[0184] A 300-ml flask was charged with 7.8 g of Monomer 5, shown below,and 12.2 g of tert-butyl α-trifluoromethylacrylate, which were dissolvedin 8.5 g of toluene. The system was fully purged of oxygen, charged with0.34 g of the initiator AIBN, and heated at 60° C. at whichpolymerization reaction took place for 24 hours.

[0185] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 2 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 16.0 g of a white polymer, which was foundto have a Mw of 7,900 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.4 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 5 andtert-butyl α-trifluoromethylacrylate in a molar ratio of 61:39.

Synthesis Example 8

[0186] Copolymerization of Monomer 6 and tert-butylα-trifluoromethylacrylate (6:4)

[0187] A 300-ml flask was charged with 10.3 g of Monomer 6, shown below,and 9.7 g of tert-butyl α-trifluoromethylacrylate, which were dissolvedin 8.5 g of toluene. The system was fully purged of oxygen, charged with0.27 g of the initiator AIBN, and heated at 60° C. at whichpolymerization reaction took place for 24 hours.

[0188] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 2 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 16.4 g of a white polymer, which was foundto have a Mw of 8,100 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.4 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 6 andtert-butyl α-trifluoromethylacrylate in a molar ratio of 62:38.

Synthesis Example 9

[0189] Copolymerization of Monomer 7 and tert-butylα-trifluoromethylacrylate (6:4)

[0190] A 300-ml flask was charged with 10.5 g of Monomer 7, shown below,and 9.5 g of tert-butyl α-trifluoromethylacrylate, which were dissolvedin 8.5 g of toluene. The system was fully purged of oxygen, charged with0.27 g of the initiator AIBN, and heated at 60° C. at whichpolymerization reaction took place for 24 hours.

[0191] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 2 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 15.7 g of a white polymer, which was foundto have a Mw of 7,700 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.5 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 7 andtert-butyl α-trifluoromethylacrylate in a molar ratio of 60:40.

Synthesis Example 10

[0192] Copolymerization of Monomer 8 and tert-butylα-trifluoromethylacrylate (6:4)

[0193] A 300-ml flask was charged with 7.9 g of Monomer 8, shown below,and 12.1 g of tert-butyl α-trifluoromethylacrylate, which were dissolvedin 8.5 g of toluene. The system was fully purged of oxygen, charged with0.34 g of the initiator AIBN, and heated at 60° C. at whichpolymerization reaction took place for 24 hours.

[0194] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 2 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 16.2 g of a white polymer, which was foundto have a Mw of 8,300 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.4 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 8 andtert-butyl α-trifluoromethylacrylate in a molar ratio of 61:39.

Synthesis Example 11

[0195] Copolymerization of Monomer 9 and tert-butylα-trifluoromethylacrylate (6:4)

[0196] A 300-ml flask was charged with 10.3 g of Monomer 9, shown below,and 9.7 g of tert-butyl α-trifluoromethylacrylate, which were dissolvedin 8.5 g of toluene. The system was fully purged of oxygen, charged with0.27 g of the initiator AIBN, and heated at 60° C. at whichpolymerization reaction took place for 24 hours.

[0197] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 2 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 16.0 g of a white polymer, which was foundto have a Mw of 8,100 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.5 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 9 andtert-butyl α-trifluoromethylacrylate in a molar ratio of 62:38.

Synthesis Example 12

[0198] Copolymerization of Monomer 10 and tert-butylα-trifluoromethylacrylate (6:4)

[0199] A 300-ml flask was charged with 10.5 g of Monomer 10, shownbelow, and 9.5 g of tert-butyl α-trifluoromethylacrylate, which weredissolved in 8.5 g of toluene. The system was fully purged of oxygen,charged with 0.27 g of the initiator AIBN, and heated at 60° C. at whichpolymerization reaction took place for 24 hours.

[0200] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 2 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 16.3 g of a white polymer, which was foundto have a Mw of 7,400 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.4 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 10 andtert-butyl α-trifluoromethylacrylate in a molar ratio of 61:39.

Synthesis Example 13

[0201] Copolymerization of Monomer 11, Monomer 6 and tert-butylα-trifluoromethylacrylate (2:4:4)

[0202] A 300-ml flask was charged with 4.3 g of Monomer 11, shown below,9.6 g of Monomer 6, and 6.1 g of tert-butyl α-trifluoromethylacrylate,which were dissolved in 8.5 g of toluene. The system was fully purged ofoxygen, charged with 0.26 g of the initiator AIBN, and heated at 60° C.at which polymerization reaction took place for 24 hours.

[0203] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 2 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 15.5 g of a white polymer, which was foundto have a Mw of 8,400 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.4 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 11, Monomer6 and tert-butyl α-trifluoromethylacrylate in a molar ratio of 22:41:37.

Synthesis Example 14

[0204] Copolymerization of Monomer 11, Monomer 9 and tert-butylα-trifluoromethylacrylate (2:4:4)

[0205] A 300-ml flask was charged with 4.3 g of Monomer 11, 9.6 g ofMonomer 9, and 6.1 g of tert-butyl α-trifluoromethylacrylate, which weredissolved in 8.5 g of toluene. The system was fully purged of oxygen,charged with 0.26 g of the initiator AIBN, and heated at 60° C. at whichpolymerization reaction took place for 24 hours.

[0206] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 2 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 16.2 g of a white polymer, which was foundto have a Mw of 8,400 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.4 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 11, Monomer9 and tert-butyl α-trifluoromethylacrylate in a molar ratio of 20:43:37.

Synthesis Example 15

[0207] Copolymerization of Monomer 11, Monomer 6 and 2-ethyladamantylα-trifluoromethylacrylate (2:4:4)

[0208] A 300-ml flask was charged with 3.8 g of Monomer 11, 8.4 g ofMonomer 6, and 7.8 g of 2-ethyladamantyl α-trifluoromethylacrylate,which were dissolved in 8.5 g of toluene. The system was fully purged ofoxygen, charged with 0.22 g of the initiator AIBN, and heated at 60° C.at which polymerization reaction took place for 24 hours.

[0209] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 2 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 15.9 g of a white polymer, which was foundto have a Mw of 8,100 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.4 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 11, Monomer6 and 2-ethyladamantyl α-trifluoromethylacrylate in a molar ratio of19:41:40.

Synthesis Example 16

[0210] Copolymerization of Monomer 11, Monomer 9 and 2-ethyladamantylα-trifluoromethylacrylate (2:4:4)

[0211] A 300-ml flask was charged with 3.8 g of Monomer 11, 8.4 g ofMonomer 9, and 7.8 g of 2-ethyladamantyl α-trifluoromethylacrylate,which were dissolved in 8.5 g of toluene. The system was fully purged ofoxygen, charged with 0.22 g of the initiator AIBN, and heated at 60° C.at which polymerization reaction took place for 24 hours.

[0212] The polymer thus obtained was worked up by pouring the reactionmixture into hexane whereupon the polymer precipitated. The procedure ofdissolving the polymer in THF and pouring in 2 liters of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 16.4 g of a white polymer, which was foundto have a Mw of 7,700 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.5 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of Monomer 11, Monomer9 and 2-ethyladamantyl α-trifluoromethylacrylate in a molar ratio of21:41:38.

[0213] Evaluation

[0214] Polymer Transmittance Measurement

[0215] The polymers obtained in Synthesis Examples 1 to 16, designatedPolymers 1 to 16, respectively, were determined for transmittance. Threeother polymers were furnished for comparison purposes. ComparativePolymer 1 is a monodisperse polyhydroxystyrene having a molecular weightof 10,000 and a dispersity (Mw/Mn) of 1.1 in which 30% of hydroxylgroups are replaced by tetrahydropyranyl groups. Similarly, ComparativePolymer 2 is polymethyl methacrylate having a molecular weight of 15,000and a dispersity (Mw/Mn) of 1.7; and Comparative Polymer 3 is a novolacpolymer having a meta/para ratio of 40/60, a molecular weight of 9,000and a dispersity (Mw/Mn) of 2.5.

[0216] Each polymer, 1 g, was thoroughly dissolved in 20 g of propyleneglycol monomethyl ether acetate (PGMEA), and passed through a 0.2-μmfilter, obtaining a polymer solution. The polymer solution was spincoated onto a MgF₂ substrate and baked on a hot plate at 100° C. for 90seconds, forming a polymer film of 100 nm thick on the substrate. Usinga vacuum ultraviolet spectrometer (VUV-200S by Nihon Bunko Co., Ltd.),the polymer layer was measured for transmittance at 248 nm, 193 nm and157 nm. The results are shown in Table 1. TABLE 1 Transmittance (%) 248nm 193 nm 157 nm Polymer 1 99 91 59 Polymer 2 99 90 55 Polymer 3 99 9158 Polymer 4 99 90 54 Polymer 5 99 14 54 Polymer 6 99 14 53 Polymer 7 9991 57 Polymer 8 99 90 50 Polymer 9 99 91 61 Polymer 10 99 90 58 Polymer11 99 91 52 Polymer 12 99 90 61 Polymer 13 99 90 51 Polymer 14 99 91 52Polymer 15 99 90 48 Polymer 16 99 91 49 Comparative Polymer 1 90 5 15Comparative Polymer 2 91 80 12 Comparative Polymer 3 82 6 17

[0217] It is evident from Table 1 that resist materials using theinventive polymers maintain sufficient transparency at the F₂ excimerlaser wavelength (157 nm).

[0218] Resist Preparation and Exposure

[0219] Resist solutions were prepared in a conventional manner bydissolving amounts as shown in Table 2 of the polymer, photoacidgenerator (PAG1 or PAG2), basic compound, and dissolution inhibitor(DRI1) in 1,000 parts of propylene glycol monomethyl ether acetate(PGMEA).

[0220] On silicon wafers having a film of DUV-30 (Brewer Science) coatedto a thickness of 85 nm, the resist solutions were spin coated, thenbaked on a hot plate at 120° C. for 90 seconds to give resist filmshaving a thickness of 100 nm.

[0221] The resist films were exposed by means of an F₂ excimer laser(VUVES 4500 by Lithotec Japan Co., Ltd.) while varying the exposuredose. Immediately after exposure, the resist films were baked (PEB) at120° C. for 90 seconds and then developed for 60 seconds with a 2.38%aqueous solution of tetramethylammonium hydroxide. The film thicknesswas measured in different dose areas. From the residual filmthickness-to-dose relationship, the sensitivity (Eth) was determined asthe exposure dose giving a film thickness 0. A γ value which was theslope (tanθ) of the characteristic curve was also determined.

[0222] Separately, through a mask having a Cr pattern formed on a MgF₂substrate, the resist film in close contact with the Cr pattern surfacewas exposed to a F₂ laser for effecting contact exposure. The exposurewas followed by similar PEB and development, forming a pattern. A crosssection of the pattern was observed under SEM, the ascertainable minimumpattern size giving a resolution. TABLE 2 Photoacid Basic DissolutionPolymer generator compound inhibitor (pbw) (pbw) (pbw) (pbw) Solvent(pbw) Eth, mJ/cm² γ Polymer 1 PAG1 tributylamine — PGMEA 10 15 (100) (4)(0.1) (1000) Polymer 2 PAG1 tributylamine — PGMEA 8 18 (100) (4) (0.1)(1000) Polymer 3 PAG1 tributylamine — PGMEA 6 10 (100) (4) (0.1) (1000)Polymer 4 PAG1 tributylamine — PGMEA 4 12 (100) (4) (0.1) (1000) Polymer5 PAG1 tributylamine — PGMEA 3.2 10 (100) (4) (0.1) (1000) Polymer 6PAG1 tributylamine — PGMEA 2.2 15 (100) (4) (0.1) (1000) Polymer 1 PAG1triethanolamine — PGMEA 10 25 (100) (4) (0.1) (1000) Polymer 1 PAG1tributylamine DRI1 PGMEA 6 15 (100) (4) (0.1) (10) (1000) Polymer 1 PAG2tributylamine — PGMEA 8 26 (100) (4) (0.1) (1000) Comparative PAG1triethanolamine — PGMEA non- — Polymer 1 (4) (0.1) 1000 sensitive,turned negative without film thickness decreasing to 0 nm

[0223] Upon exposure to VUVES, the resist compositions within the scopeof the invention exhibited high gamma values and high contrast andexerted the positive working effect that the film thickness decreasedwith an increasing exposure dose. The resolving power upon contactexposure was high.

[0224] Japanese Patent Application Nos. 2002-083807 and 2002-084033 areincorporated herein by reference.

[0225] Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A polymer comprising recurring units each having a functional groupof the following general formula (1), and having a weight averagemolecular weight of 1,000 to 500,000,

wherein R¹ is a methylene group, oxygen atom, sulfur atom or SO₂, R² toR⁵ each are hydrogen, fluorine, a straight, branched or cyclic alkyl orfluorinated alkyl group of 1 to 20 carbon atoms, —R⁶—SO₃R⁷ or —R⁶—SO₂R⁷,at least one of R² to R⁵ containing —R⁶—SO₃R⁷ or —R⁶—SO₂R⁷, R⁶ is avalence bond or a straight, branched or cyclic alkylene or fluorinatedalkylene group of 1 to 20 carbon atoms, R⁷ is fluorine or a straight,branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms whichmay contain a hydrophilic group such as hydroxyl, and “a” is 0 or
 1. 2.The polymer of claim 1 wherein said recurring units are recurring unitsof either one of the following general formulae (2a) to (2d):

wherein R⁸ to R¹⁰ and R¹⁸ to R²⁰ each are hydrogen, fluorine or astraight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 20carbon atoms, R¹¹ is a group of the above formula (1), R¹² is amethylene group, oxygen atom, sulfur atom or SO₂, R¹³ to R¹⁶ each arehydrogen, fluorine, —R¹⁷—OR¹¹, —R¹⁷—CO₂R¹¹ or a straight, branched orcyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms, atleast one of R¹³ to R¹⁶ containing —R¹⁷—OR¹¹ or —R¹⁷—CO₂R¹¹, R¹⁷ and R²¹each are a valence bond or a straight, branched or cyclic alkylene orfluorinated alkylene group of 1 to 20 carbon atoms, R²² is a straight,branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms, b is0 or 1, c is 1 or 2, and d is an integer of 0 to 4, satisfying 1≦c+d≦5.3. A polymer comprising recurring units of the following general formula(3) and having a weight average molecular weight of 1,000 to 500,000,

wherein R²³ is a methylene group, oxygen atom, sulfur atom or SO₂, R²⁴to R²⁷ each are hydrogen, fluorine, —R²⁸—SO₂F, —R²⁸—SO₃R²⁹ or astraight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 30carbon atoms, at least one of R²⁴ to R²⁷ containing —R²⁸—SO₂F or—R²⁸—SO₃R²⁹, R²⁸ is a valence bond or a straight, branched or cyclicalkylene or fluorinated alkylene group of 1 to 20 carbon atoms, R²⁹ isan acid labile group, an adhesive group or a straight, branched orcyclic fluorinated alkyl group of 1 to 20 carbon atoms which may containa hydrophilic group such as hydroxyl, and e is 0 or
 1. 4. The polymer ofclaim 1, further comprising recurring units of the following generalformula (4):

wherein R³⁰ is a methylene group, oxygen atom, sulfur atom or SO₂, R³¹to R³⁴ each are hydrogen, fluorine, —R³⁵—OR³⁶, —R³⁵—CO₂R³⁶ or astraight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 20carbon atoms, at least one of R³¹ to R³⁴ containing —R³⁵—OR³⁶ or—R³⁵—CO₂R³⁶, R³⁵ is a valence bond or a straight, branched or cyclicalkylene or fluorinated alkylene group of 1 to 20 carbon atoms, R³⁶ ishydrogen, an acid labile group, an adhesive group or a straight,branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms whichmay contain a hydrophilic group such as hydroxyl, and f is 0 or
 1. 5.The polymer of claim 4 wherein the recurring units of formula (4) have astructure of the following formula (4a) or (4b):

wherein R³⁶ is as defined above, R³⁷ to R⁴⁰ each are hydrogen, fluorineor an alkyl or fluorinated alkyl group of 1 to 4 carbon atoms, at leasteither one of R³⁷ and R³⁸ contains at least one fluorine atom, and atleast either one of R³⁹ and R⁴⁰ contains at least one fluorine atom. 6.The polymer of claim 1, further comprising recurring units of thefollowing general formula (5):

wherein R⁴¹ is hydrogen, fluorine or a straight, branched or cyclicalkyl or fluorinated alkyl group of 1 to 20 carbon atoms, R⁴² is avalence bond or a straight, branched or cyclic alkylene or fluorinatedalkylene group of 1 to 20 carbon atoms, R⁴³ is hydrogen or an acidlabile group, R⁴⁴ is fluorine or a straight, branched or cyclicfluorinated alkyl group of 1 to 20 carbon atoms, g is 1 or 2, and h isan integer of 0 to 4, satisfying 1≦g+h≦5.
 7. The polymer of claim 6wherein the recurring units of formula (5) have the following formula(5a) or (5b):

wherein R⁴³ is as defined above, R⁴⁵ to R⁵⁰ each are hydrogen, fluorineor an alkyl or fluorinated alkyl group of 1 to 4 carbon atoms, at leasteither one of R⁴⁵ and R⁴⁶ contains at least one fluorine atom, at leasteither one of R⁴⁷ and R⁴⁸ contains at least one fluorine atom, and atleast either one of R⁴⁹ and R⁵⁰ contains at least one fluorine atom. 8.The polymer of claim 1, further comprising recurring units of thefollowing general formula (6):

wherein R⁵¹ to R⁵³ each are hydrogen, fluorine or a straight, branchedor cyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms, andR⁵⁴ is hydrogen, an acid labile group, an adhesive group or a straight,branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms whichmay contain a hydrophilic group such as hydroxyl.
 9. The polymer ofclaim 8 wherein R⁵³ in formula (6) is trifluoromethyl.
 10. A resistcomposition comprising the polymer of claim
 1. 11. A chemicallyamplified positive resist composition comprising (A) the polymer ofclaim 1, (B) an organic solvent, and (C) a photoacid generator.
 12. Theresist composition of claim 11, further comprising (D) a basic compound.13. The resist composition of claim 11, further comprising (E) adissolution inhibitor.
 14. A process for forming a resist patterncomprising the steps of: applying the resist composition of claim 11onto a substrate to form a coating, heat treating the coating and thenexposing it to high-energy radiation in a wavelength band of 100 to 180nm or 1 to 30 nm through a photomask, and optionally heat treating theexposed coating and developing it with a developer.
 15. The patternforming process of claim 14 wherein the high-energy radiation is an F₂laser beam, Ar₂ laser beam or soft x-ray.